Pulpstone



L A T E N O S P P E J N G PULPSTONE 4 Sheets-Sheet 2 Filed Aug. 2'7, 1947 Inventors George Ndepnsan Wallace. L. Home 9 3135 G. N. JEPPSON ET AL PULPSTONE 4 Shets-Sheet 3 Filed Aug. 27, 1947 [ml/enters George N. deppson WaLLace L. Houa G. N. JEPPSON ET AL Jam. 4,,

PULPSTONE 4 Sheets-Sheet 4 Filed Au 27, 1947 In ven ors George H. deppson WaLLace 1.. Howe Attorney Patented .Fan. 24, 19 5 Howe, West Boylston, Mass., assignors to Norton Company;Worcester, Mass., a corporation of Massachusetts Application August 27, 1947, Serial No. 770,888

4 Claims.

The invention relates to pulpstones. One object of the invention is to provide a simple and inexpensive pulpstone construction of the type having a plurality of abrasive blocks permanently secured to a rigid center. Another object cf-the invention is'to provide a pulpstone that can be quickly manufactured. Another object of the invention-is to provide a pulpstone construction which can be embodied in a pulpstonehaving very small blocks, thus reducing the internal heat stresses which tend to rupture larger blocks or segments, and also. permitting the manufacture of a pulpstonehaving a small volume of abrasive thereby reducing the cost of the stone. Another object of the invention is to provide apulpstone construction altogether eliminating the use of holding boltsanchored to or embedded in the abrasive blocks, the ,use of which, up to the time of our invention, has been universal in practice with poured concrete center pulpstones and the use oi which has involved a considerable item of expense in the manufacture of such pulpstones. M n I Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists. in the features of construction, combinations of elements and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims. a

In the accompanying drawings illustrating several of the many possible embodiments of the mechanical features of the invention,

Figure 1 is a fragmentary end elevationofa pulpstone constructed in accordance with the invention.

Figure 2 is a fragmentary view of the surface of the pulpstone of Figure 1. r

Figure 3 is an axial sectional view of approximately one half of the pulpstone on an enlarged scale, the section being taken along the line 33ofFigure2. l p

Figures 4, 5 and 6 are endelevations similar to Figure 1 showing modifications of the invention. a 1

. T e, t p o pu oe zt h th in ntion e a s. i. h 5 9155 9 .1 5? pu l-s g s Mi li by arranginga number of abrasive blocks, sometimes a l d s m s t0 h aee s er rl s; ea ar na. sl nt n the blacks t ethe such. arrangement, locating a mold sleeve pit the ik in s e 9 h sl ttea d as name s retr bet enthe last and he p l a form the center. The hole left by the mold (c1. sh-206.4)

a '2 sleeve is the mounting hole for the pulpstone or in. some cases the sleeve around which the concrete is molded may remain as part of the pulpstone. Pulpstones of this general type are disclosed in .U. S..Letters .Patent to Jeppson No. 2,032,484 of March .3,.193.6, .U. S. Letters Patent to Larsson No. 2,074,114. of March 16, 1937, U. S. Letters Patent to Larsson No. 2,141,608 of ,December 27, 1938, U. S. Letters Patent to Howe 8; Washburn, No.;2,42l,885 of June 10, 1947 and U. S. Letters Patent to Howe 8; Washburn, No. 2,421,886 of June 10, .1947. In these patents and elsewherethere has beendisclosed the manner of assembling the abrasive blocks, separating them with sheets. offiller material such as described in U. S. Letters Patentto Larsson No. 2,654,771, clamping theblockstogether, placing themoldsleeve in position and locating a steel cagemade of series oiconcentric hoopsbetween e bloc s endt emol s an p u i t e concrete to form the pulpstone center and, aiter the concretehas set, heating theentire assembly to bake or vulcanize the filler material. Therefore we will not describesuch steps herein since they are now well known to, the art, and the present invention will be made quite clear by a description of the features. of construction, combinations of elements and arrangements of parts. Referring now to Figures 1, 2 and 3, we provide a plurality of abrasive blocks it which may be of the same shape and which shape is a feature of this invention. The abrasive may be of any suitable type such as fused alumina or silicon carbide bonded with vitrified bond all as explained in considerable detail-in the above mentioned patents. Each block it! has an outer'surface which is a segment of a cylinder. Each block It has side surfaces 12- which are preferably-in planes neither parallel to nor perpendicular to the aXi-softhe pulpstone. This shape is to'preclude any-series of joints from lying in-a circle.-- The joints are filled with fil1er ma terial 53 such as described in the Larsson Patent No. 2,054,771 andthe filler: material is non-abrad-r ing so it is desired, that this filler material shall not form a complete circle anywhere on thesurface of the .pulpstoneinorderthat, as thel ulp; stone revolves, itshall give an abrading action ov ole le g h,- q ilarein l l s; l9 p even a han ide lg ap sl e which re i planes perpendicular to the axis of the pulpqf l r "-.-L. j m r M F' ach block it further has a large end face l4 and a v similar end-face 15, each .of said races [4, and l 5 lying substantially in radial planes of the pulpstone. The inner surface [6 of each of the blocks iii consists of a series of projections l1 separated by a series of grooves 18, both projections and grooves extending clear across the face l6 in an axial direction. Preferably the sides of the projections ii are parallel and are perpendicular to the bottoms of the grooves H8. The projections ii are in effect wide teeth. The tops of the projections or teeth H are substantially in a plane which plane is non-parallel to a plane tangent to the surface ll of the particular block l8. The parallel sides of the projections or teeth it; are at angles to radial planes of the pulpstone passing through any part of the parallel sides. When the concrete is poured to form the concrete center "20 it becomes keyed to the blocks iii. In other words no block it can be removed from the concrete center without breaking some of the concrete or projections 21 thereof which extend into the grooves I8.

An important feature of the present invention is that the blocks iii are not only keyed to a greater or lesser extent to the concrete center 20, but they are also strongly held thereto by adhesive forces. The surfaces of the blocks II] are porous and somewhat rough everywhere, owing to the fact that the blocks are made by mixing hard abrasive material with powdered ceramic bond, moulding and vitrifying, which results in a certain porosity of the blocks, which can be varied, but it is never zero. Surfaces of such bonded abrasive material are well adapted to being secured by an adhesive.

On the other hand, the adhesive strength of a concrete mix, such as a 1:111 mix, that is equal parts by weight of Portland cement, sand and trap rock, is not in itself sufficient. We have found that by greatly increasing the area of contact between the blocks and the concrete sufficient holding power can be developed to hold the blocks iii in place. The 12121 mix has high adhesive strength for concrete.

The construction described eliminates the use of the various types of holding bolts disclosed in the aforementioned patents, all of which types are expensive. For reinforcement of the center 20 we preferably provide a plurality of steel hoops 25, 2B and 27, the hoops 25 being of the largest diameter, the hoops 28 being of somewhat smaller diameter, and the hoops 21' being of the smallest diameter, all as is clearly apparent from a comparison of Figures 1 and 3. The sets of hoops 25, 2t and 27 are held together in the form of cages by means of spacing and supporting irons 30 as clearly shown in Figure 3. These cages lie within and reinforce the concrete center 20.

As further reinforcement we preferably provide U-shaped irons 3i having bent-over ends 32 which may be wired by wires 33 to the hoops 23 before the concrete is poured. The bent-over ends 32 are located close to the surfaces 14 of the blocks 16 and in the angle between said surfaces and the surfaces H3 to reinforce the concrete where it extends to the greatest radial distance. These U-shaped irons 3i measurably add to the strength of the pulpstone, but they are relatively inexpensive since no turning or threading operation need be performed upon them.

One feature of the pulpstone of Figures 1 to 3 is that if mounted for revolution in the direction of the arrow in Figure 1, the surfaces M of the blocks i projecting inwardly between the adjacent blocks form large driving surfaces to preclude destruction of the pulpstone from the high torque involved when the grinding operation is heavy.

Modifications of the invention may be made as illustrated in Figure 4, 5 and 6 which we do not intend, however, to be limiting since other variations and modifications may be made.

Referring now to Figure 4, blocks 4*) have, centrally located on their inside surfaces 4 I, a pair of projections 42 extending farthest inwardly and separated by a groove 43. Spaced from these projections 42 by grooves 44 are projections 45 extending not quite so far inwardly. Spaced from these projections 45 by grooves 46 are projections 6'! which are stepped back still further and which lie adjacent to the faces Ma and lid. In this construction there is some, but not a great deal of, interlocking between the concrete 2G and the blocks 48; however, there is a large area of contact for adhesion and there are many surfaces to absorb the driving torque. We have discovered that whereas too pronounced interlocking is apt to cause fracture of the concrete, attachment by extensive surfaces in adhesive engagement with the concrete does not cause fracture either of the concrete or of portions of the blocks under the torque load now customarily encountered in paper mills.

Referring to Figure 5 another modification is disclosed in which blocks 50 have inside surfaces 5i with single center projections 52 separated by grooves 53 from a pair of stepped back projections 56 which are separated by grooves 55 from a pair of further stepped back projections 56 leaving space for large concrete projections 5'! between adjacent blocks. This construction also embodies all of the features above noted in that there is some interlocking, a great deal of surface area for adhesive attachment and many opposed radial surfaces for the driving torque.

The modification shown in Figure 6 is particularly desirable where a highly economical pulpstone is wanted and of low initial cost. The blocks 66 have inside faces 6| with projections 62 whose ends are in a plane separated by grooves 6'5 whose bottoms are in a plane and these planes are parallel to planes tangent to the outer surfaces ll of the blocks SE at the mid points thereof. Thus the pulpstone of Figure 6 can be used until almost all of the abrasive material has been worn away. The blocks 68 can be made as thin as desired in a radial direction. Some mills want a pulpstone of low initial cost even though the cost of grinding in terms of pulpstone Wear is slightly higher than if they bought a more expensive stone in the first place. In the construction shown in Figure 6 there is some, but not very much, interlocking between the concrete center and the blocks 60, but there is a great deal of surface area for adhesive attachment. The stone of Figure 6 has radial driving areas formed by the sides of the projections or teeth 62 and the sides of the concrete teeth in the grooves 63, but not such great total area as in the case of the other embodiments of the invention.

The function of the various projections or teeth and grooves is largely to make indented surfaces to increase the surface area of contact between the abrasive blocks and the concrete center 20 to increase the holding force due to adhesion. Furthermore in the case of the pulpstone of Figures 1 to 3, the surfaces M are in adhesive engagement with the concrete center 20. The increase in the surface area by reason of the indentation may be calculated on the assumption that the pulpstone ceases to be useful when the blocks have been worn down to expose some of the concrete center 20. Blocks which would leave no abrasive embedded in the concrete when the concrete first became exposed would be blocks having inner surfaces collectively forming a cylinder. The simplest approximation to such blocks would be blocks'whose inner surfaces are planes forming chords of'such cylinder. In each of the embodiments of the invention such chord planes can be measured. Since in the i1- lustrative embodiments of the invention there are no indentations in an axial direction the areas of such chord planes are proportional to the chord lengths thereof. The ratio of the indented surface area of a block of Figure l to the chord plane area is therefore found by measuring the chord length at the deepest indentation and comparing it with the total length along the indentations. Thus in Figure l we measure from junction to junction of the blocks and find the chord length and then we measure the total length along the indentations of surface [6 plus the length of the surface M in contact with the concrete 20. The ratio of the chord length to the indentation length in Figure l is 3 to 7.1. Therefore the ratio of the chord surface to the indented surface is 3 to 7.1. In Figure 4 we measure the chord length across the bottoms of the grooves 6 and we measure the indented length following each projection and groove and the walls thereof. In Figure 4 the chord length is to the indented length as 2.8 to 6.7 and therefore the chord surface is to the indented surface as 2.8 to 6.7. Similarly in Figure 5 we find the chord area is to the indented area as 2.4 to 5. And in Figure 6 we find the chord area is to the indented area as 3.2 to 6. The smallest increase of the indented surface as compared with the chord surface is in the case of Figure 6 where 6 divided by 3.2 equals 1 We prefer that the ratio of indented surface area to chord surface area shall be at least 1%. Thereby sufficient holding power is developed to hold the blocks in place. A higher factor than 1% is desirable but on the other hand it is desirable to leave as little of the abrasive blocks embedded in the concrete when the concrete is first exposed as is possible. Therefore modifications such as illustrated and others can be made of the invention to suit different requirements for pulpstones for conditions in different mills provided the above factor is at least 1'7 Another feature of the invention is that the increase in surface area due to the indentation is achieved without forming any narrow necks either in the abrasive blocks or in the concrete. For example, the projections 51 of concrete in Figure 5 can be called dovetails but they definitely do not have narrow portions. The ends of these dovetails 57 are nearly as Wide as the narrowest portions at the bases. Thus pulpstones according to the present invention rely for holding the blocks to the centers especially on the adhesion of concrete to vitrified abrasive material. There is preferably som interlocking between the concrete and the vitrified abrasive material. In all cases projections of concrete extend into depressions of vitrified abrasive material and projections of vitrified abrasive material extend into depressions of concrete. In all embodiments except that of Figure 6 there is considerable interlocking of such projections and depressions. But preferably there are no projeciii) tions of concrete or ab'r'asive having sections which have less than four-fifths of the area of the largest sections of suchprojectidns.

It will thus-be seen 'that'ther'e has been provided by "this invention a pulpstone in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be -made of the above invention and as many changes might be made in thejernbodiments above set forth, it is to be understood that all matters hereinb efore set forth or shown in the accompanying -drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. A pulpstone comprising a plurality of blocks of vitrified bonded abrasive material having an outer cylindrical surface, a concrete core in adhesive engagement with inner surfaces of said blocks, each inner surface of each block being indented where it is in contact with the concrete and the surface area of each block in adhesive engagement with the concrete having a ratio of at least one and seven-eighths to the area of a chord plane at the deepest indentation, reinforcing irons in the concrete core parts of which extend to a further radial distance than the innermost portions of the blocks, there being substantial interlocking of the concrete core with the vitrified bonded abrasive blocks, there being projections of concrete extending into depressions in the vitrified abrasive material and projections of vitrified abrasive material extending into depressions in the concrete, but no projections of concrete or vitrified abrasive material having sections which have less area than four-fifths of the area of the largest sections of such projections, and at least one-third of the concrete being Portland cement.

2. A pulpstone comprising a plurality of blocks of vitrified bonded abrasive material having an outer cylindrical surface, a concrete core in adhesive engagement with inner surfaces of said blocks, each inner surface of each block being indented where it is in contact with the concrete and the surface area of each block in adhesive engagement with the concrete having a ratio of at least one and seven-eighths to the area of a chord plane at the deepest indentation, and at least one-third of the concrete being Portland cement.

3. A pulpstcne comprising a plurality of blocks of vitrified bonded abrasive material having an outer cylindrical surface, a concrete core in adhesive engagement with inner surfaces of said blocks, each inner surface of each block being indented where it is in contact with the concrete and the surface area of each block in adhesive engagement with the concrete having a ratio of at least one and seven-eighths to the area of a chord plane at the deepest indentation, reinforcing irons in the concrete core parts of which extend to a further radial distance than the innermost portions of the blocks, and at least one-third of the concrete being Portland cement.

4. A pulpstone comprising a plurality of blocks of vitrified bonded abrasive material having an outer cylindrical surface, a concrete core in adhesive engagement with inner surfaces of said blocks, each inner surface of each block being indented where it is in contact with the concrete and the surface area of each block in adhesive engagement with the concrete having a ratio of at least one and seven-eighths to the area of a chord plane at the deepest indentation, there 8 being substantial interlocking of the concrete core with the vitrified bonded abrasive blocks, REFERENCES CITED there being projections of concrete extending into The following references are of record in the depressions in the vitrified abrasive material and file of this patent: projections of vitrified abrasive material extend- 5 ing into depressions in the concrete, but no pro- UNITED STATES PATENTS jections of concrete or vitrified abrasive material Number Name Date having sections which have less area than four- Re. 15,097 Solan et a1 Apr. 26, 1921 fifths of the area of the largest sections of such 2,119,412 Ball et a1 May 31, 1938 projections, and at least one-third of the con- 10 2,141,608 Larsson Dec. 27, 1938 crete being Portland cement. ,205,296 Leafe June 18, 1940 GEORGE N. JEPPSON. WALLACE L. HOWE. 

